A variety of devices are known for use in the chucks of rotary power tools, such as hand held electric drills, to reduce the ingress of dust and cuttings from into the chuck mechanism. Elastomeric caps have been described for use at the bit receiving portion of a chuck barrel as dust guards to keep cuttings out of the chuck mechanism, as in Thessig et. al. U.S. Pat. No. 4,664,394, for the purposes of gripping the bit, as in Whitehead U.S. Pat. No. 4,575,108, and for achieving both bit centering and dust protection, Huff et. al. U.S. Pat. 5,135,241.
Such previously known elastomeric caps are subject to damage, for example, by being cut by the sharp edges of cuttings directed against the elastomeric material by the tool bit. Such elastomeric dust seals tend to abrade and wear where they contact the shank of the tool bit during normal use. Also, elastomeric dust seals may become brittle during extended use due to the heat conducted to the dust seal from the bit. Finally, in some cases elastomeric dust seals may be unable to readily conform to the flutes in the bit, and may thus permit dust or cuttings to enter the chuck through those flutes.
It is therefore an object of the present invention to provide a tool chuck having a dust seal constructed of a resilient, high strength material that is less likely to sustain damage from the sharp edges of cuttings emanating from the workpiece.
It is another object of the present invention to provide a tool chuck having a removable dust seal that can be easily replaced during the lifetime of the tool chuck to provide a high degree of protection against the ingress of dust and cuttings into the chuck mechanism.
It is still another object of the present invention to provide a tool chuck having a dust seal that readily conforms to the shape of the tool bit, for example, by extending into the flutes of the tool bit, to thereby enhance the dust-protecting feature of the tool chuck.